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Earth-like planet just a ‘stroll’ away? Sci-fi knew that all along

In “Another Earth,” that other planet was right over the horizon. (Fox Searchlight Pictures)

We’re in no danger of a Crisis on Infinite Earths, but the discovery of an Earth-like planet just 13 light-years away from our home sparks theories about similar planets that might reside in our galaxy — or, for the deep thinkers, even in other dimensions.

Alternate or similar Earths are commonplace in science fiction, scratching the same itch as speculative fiction and alternate histories — for instance, the longstanding “Elseworld” and “What-If?” offshoots from DC and Marvel. Below are some standout examples of Earth’s similar — yet entirely different — from our own, but feel free to add your own favorites in the comments below!

“Star Trek’s” “Mirror, Mirror”: One of the influential examples of an alternate universe, “Mirror, Mirror” not only introduced the crew of the Enterprise to evil versions of themselves, the I.S.S. (instead of U.S.S.) Enterprise and the Terran Empire, but also introduced fans to the much-parodied “evil goatee” indicating alternate Spock’s surly disposition.

“Crisis on Infinite Earths”: The parallel-Earth story to end them all, DC’s dimension-spanning crossover revolutionized the DC universe, drastically altering 50 years of built-up continuity in exchange for a slimmer, more simplified universe. Prior to “Infinite Earths,” DC had explained away the varied characterizations and inconsistent storylines by placing everything in the “multiverse,” so that Golden Age heroes could still fight crime without rubbing elbows with, say, an evil version of the Justice League: They each existed on their own Earth.

After 12 issues and a climactic battle with the Anti-Monitor, the multiverse was condensed into a single, amalgamated universe that gave DC a clean slate to continue its storytelling. Later on, in typical comics fashion, that simplification eventually led to complicated crossover events such as “Infinite Crisis” and “Final Crisis.”

“Fringe’s” alternate Earth: Much of the show’s underlying plot revolves around scientist Walter discovering a way to enter an alternate dimension, one in which his son Peter in still alive. Taking Peter 2 into his own universe, Walter ends up destabilizing the alternate Earth and sparking the events of the series.

“Another Earth”: In spite of the discovery of a planet nearly identical to Earth at the beginning of the film, “Another Earth” focuses less on the exploration of another planet and more on the introspective nature of guilt and identity, with the new Earth looming ominously on the horizon.

“The Man in the High Castle”: One of science-fiction luminary Phillip K. Dick’s more sedated works, “The Man in the High Castle” hinges on a single event: the successful assassination of President Franklin D. Roosevelt in 1933, which eventually leads to the Axis powers occupying the U.S., which is split between Nazi rule in the East and Japanese rule in the West.

BioShock Infinite: Though the spiritual sequel to BioShock has yet to be released, early extended footage of the game featured a jarring glimpse into the possible involvement of parallel universes, with the player’s companion Elizabeth accidentally opening a tear in reality, revealing a neon-lit movie theater showing “Revenge of the Jedi,” the working title of “Return of the Jedi” while Tears for Fears plays in the background.

So far, the game’s director Ken Levine has remained mum about the implications of his alternate-history examination into race, religion and America also involving peeks into even more varied dimensions.

“The Twilight Zone” episode “The Parallel”: A fourth-season episode of the legendary series, “The Parallel” features an astronaut who blacks out midflight, only to return to an Earth seemingly identical to his own. But then he begins to notice minor irregularities. As with all “Twilight Zone” episodes, the less you know going in, the better.